What Is an Antrum?

Medically reviewed by Stacy Sampson, DO on February 2, 2018 — Written by Ana Gotter on February 2, 2018

An antrum is a chamber or cavity within the body. There are a number of different types of antra within each human body. They serve a unique and important purpose for every location they belong in.

Where are antra located?

We have antra in several different places in our bodies. They each serve a unique purpose.

In or near the stomach

There are two different antra that exist in or near the stomach, for example. The first is the antrum cardiacum. This is the dilation, or enlarging, that happens low in the esophagus, close to where it flows into the stomach.

The second is the pyloric antrum. It’s also commonly known as the gastric antrum. This is the wider part of the pylorus, which is the narrower part of the stomach. It resides upstream from the pyloric canal and its junction of the pyloric sphincter to the duodenum, or first part of the small intestine.

In the temporal bone of the skull

The mastoid antrum can be found in the temporal bone near the middle ear. This air-filled antrum is next to mastoid air cells. It also communicates with the middle ear. The mastoid cells are thought to affect the function of the inner and middle ear.

In the ovaries

Follicular antra are found in the ovaries. Each antral follicle contains a fluid-filled antrum and an immature egg cell. This follicle matures when it’s preparing for ovulation.

The presence of follicular antra can be analyzed as an indication of a female’s ability to get pregnant. During fertility testing, doctors may order antra follicular testing. The higher the number of follicular antra, the greater probability of pregnancy.

In the sinuses

The maxillary antrum is the largest of the paranasal sinuses. It’s commonly called the maxillary sinus, and is also known as the antrum of Highmore. It’s found within the maxillary bone next to the nose, above the teeth, and under the eyes. The maxillary sinuses open into the middle meatus of the nose.

Medical conditions that affect antra

There are a number of different medical conditions that can affect antra within the body. Almost all of these conditions will be specific to one particular type of antrum, and not the others. These conditions include:

Gastritis

Inflammation of the stomach is known as gastritis. It can involve the gastric antrum of the stomach. Some people don’t experience symptoms of gastritis. When symptoms do develop, the most common are:

nausea

vomiting

stomach cramps

indigestion

Gastritis can have many different causes, including:

smoking cigarettes

extreme stress

other injury to the stomach

Treatment will vary based on the cause.

Peptic ulcers

Peptic ulcers can also affect the gastric antrum. When this happens, they’re often called antral ulcers. These develop along the lining within this portion of the stomach.

The most common symptom of an antral ulcer is burning or gnawing abdominal pain that usually occurs right after eating. It’s sometimes even worse while eating. Other common symptoms include:

weight loss

nausea

vomiting

blood in the stool

This is a serious condition. Seek medical attention immediately.

Mastoiditis

Mastoiditis is the inflammation of the mucosal lining of the mastoid. This includes its antrum, in the air system it contains near the middle ear. It’s often the result of a middle ear infection. Symptoms can include:

ear pain

tenderness and swelling behind the ear

headache

In severe cases, drainage of yellow or brown discharge through a ruptured eardrum may occur. Treatment often involves administration of an antibiotic through an IV.

Polycystic ovarian syndrome

Several conditions, including polycystic ovarian syndrome, can affect the follicular antra by keeping the ovarian follicles from growing and maturing. This keeps the follicles from properly developing and releasing eggs, which can lead to infertility. It can be a temporary or long-term problem.

Maxillary sinusitis

This is inflammation that may be due to an infection of the maxillary sinuses. It can directly affect this area and prevent it from doing its job properly. Your doctor may prescribe antibiotic therapy if a bacterial infection is suspected. They may also recommend nasal sprays to help treat or prevent certain types of sinusitis.

The takeaway

While antrum is a general medical term that just means “chamber” or “cavity” within the body, the similarities between different types of antra basically end there.

Each type of antrum serves a unique purpose. They’re all crucial to different systems and organs within the body to function properly.